Given unreal is owned by their biggest competitor theres little to no chance of that happeng. Valve arent really a video game developer anymore, they just tinker on the side for fun.

Granted, last time Valve released a proper game was in 2020 (Alyx), but to say they are not a developer anymore isn't super fair. They take their time, and their priorities probably are elsewhere, they still do develop games.

Valorant, CS:GO's closest competitor, is in Unreal and looks similar. These games are going for high framerates and running on the majority of PCs, even ones with integrated graphics. Switching engines wouldn't do them any favors, and it would severely cripple their modding tools.